Perceptual vs. Relative Intent in Lightroom & Photoshop?

Discussion in 'Digital Darkroom' started by bdb, Dec 18, 2007.

  1. bdb

    bdb

    This is one color management issue I still don't fully understand. When
    printing to an Epson R2400 in a color-managed workflow (from Lightroom and
    Photoshop CS3), should I be selecting Perceptual or Relative? And should I
    select black point compensation (it is automatically selected in Lightroom, it
    seems).
     
  2. 1_i didtn see much difference myself, but i read that relative gave better result.

    2_yes in both case. or i should say always if you can.
     
  3. When you have an out of gamut color in your image, the relative colorimetric rendering
    adjusts just that one out of gamut color so that it is in gamut by picking the closest color
    to it that is in gamut. The perceptual rendering adjusts all the colors in your image so that
    the relationship between all the colors remains the same. To me that means that if I use
    perceptual rendering the colors might all change unpredictably. If I use relative rendering,
    the only color that might change unpredictably will be the out of gamut color.

    Peter
     
  4. Most people defaults to Relative. Another approach is before you print the image, you can use the soft proofing feature to see how the print out will look, you can switch between relative and perceptual to gauge which one you like better.
     
  5. Differences between how relative colormetric and perceptual will render an image depends a lot on the specific image dynamics. Most images will look virtually identical, but if the color values are approaching boundaries of the output paper-ink profile, you might see differences.

    There's a decent write up of Rendering Intents at Steve's Digicams:
    http://steves-digicams.com/techcorner/July_2005.html

    My default is to use relative colormetric with black point compensation enabled. It produces very nice results on the R2400 from Lightroom.

    Godfrey
     
  6. Quick search on the 'net found this:

    http://www.cambridgeincolour.com/tutorials/color-space-conversion.htm

    Tells you everything you need to know.
     
  7. I print a ton to the R2400 from Photoshop and almost ALWAYS choose Black Pt. Compensation and Perceptual. There you are. It works, tried and true.
     
  8. > 2_yes in both case. or i should say always if you can.

    The majority of the paper profiles incorporate a perceptual rendering intent that tries to make use of the whole dark range of the media, by definition.
    Therefore, since it already maps the dark colors of the media,
    enabling BPC does not affect this rendering intent much... almost always.

    Quote from "Adobe Systems' Implementation of BPC"

    http://partners.adobe.com/public/developer/en/pdf/AdobeBPC.pdf

    "Color conversion using Perceptual intent already maps source white to destination white and source black to destination black. Because this mapping preserves the relationships of the shades, it is unlikely that a whole shadow section will be mapped to the same black value. Therefore, BPC should not be necessary. BPC is available, however, for this rendering intent, to be used with malformed profiles. For a given picture, the user can decide whether using BPC improves the color conversion and can select it or deselect it accordingly."
     
  9. Always use perceptual renedering with blackpoint compensation for printing. Printer profiles
    are made for perceptual rendering by default. In order to avoid unexpected color shifts you
    should use softproofing and make sure that the out of gamut colors are brought within
    gamut (best method is selective desaturation until they are safe).

    Relative rendering should be used for converting from one color space to another, not for
    printing.
     
  10. > Printer profiles are made for perceptual rendering by default.

    Please explain?

    > ... make sure that the out of gamut colors are brought within gamut

    The essence of perceptual gamut mapping is (fixed) gamut compression of ALL colors (out-of-gamut + in-gamut).
    So why bother bringing out-of-gamut colors within gamut when using perceptual?


    > Relative rendering should be used for converting from one color space to another

    Relative colorimetric is the ONLY intent that will be applied when doing working space (matrix) conversions.
    It's not the only option you have in PS, perceptual is not grayed out, but PS WILL do a relative conversion.
     
  11. "> Printer profiles are made for perceptual rendering by default.

    Please explain?" - That's the rendering intent almost all profiling software expects to be used for printer profiles. Open up a printer profile and check what rendering intent it was made for. You'll
    notice it was made for perceptual rendering 99 out of 100 times.

    "> ... make sure that the out of gamut colors are brought within gamut

    The essence of perceptual gamut mapping is (fixed) gamut compression of ALL colors (out-of-gamut + in-gamut). So why bother bringing out-of-gamut colors within gamut when using
    perceptual?" - This way you have manual control over how the out-of-gamut colors are being rendered, while the other colors are still rendered the way the profile was designed for.

    "> Relative rendering should be used for converting from one color space to another

    Relative colorimetric is the ONLY intent that will be applied when doing working space (matrix) conversions. It's not the only option you have in PS, perceptual is not grayed out, but PS WILL do a
    relative conversion." - Yes, and I was briefly explaining why that is.
     

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